1. Field of the Invention
The present disclosure relates to Auger electron spectrometry and to electron beam apparatus.
2. Description of the Background Art
Auger spectrometry is a technique that uses a primary electron beam or other means, such as x-ray radiation, to probe a material surface. The primary electron beam or other means causes the emission of Auger electrons.
Auger electrons result from the following process in the material surface. When an electron is emitted from a core level of an atom, leaving a vacancy, an electron from a higher energy level may fall into the lower-energy-level vacancy. This results in a release of energy either in the form of an emitted photon or by ejecting another electron. Electrons ejected in this manner are called Auger electrons.
Auger electrons are detected by a spectrometer. The elements in the sample surface region may be determined from kinetic energies of the peaks in the Auger spectrum.
Auger electron spectrometers traditionally are incorporated into only non-magnetic type scanning electron microscopes (SEMs). In such SEMs, the magnetic focusing fields are either not present, fully contained or nearly fully contained inside the objective lens, and the sample is placed in a field-free or nearly field-free region below the lens. In such a system the Auger electrons travel in approximately straight lines from the sample, and the spectrometer's collection efficiency is determined largely by the solid angle of the spectrometer's entrance aperture and the spectrometer's angular position with respect to the sample surface.
Magnetic objective lenses are conventionally avoided for Auger spectrometry because such lenses typically immerse the sample in a substantial magnetic field. Due to the presence of such magnetic fields, the Auger electrons cannot travel in substantially straight and un-deflected lines from the sample surface to an Auger spectrometer, located outside the SEM column.